The symbiosis of plants and animal has always been present, but long ago a special bond was formed to make the survival of plants coincide with the survival of their caretakers.
People that live in cities no longer have any contact with the gods. There was a pact between the gods, humans, and animals. We could talk to the gods and the trees were the witness' to the pact. When the trees started getting cut down to make cities the pact was broken by the destruction of the witness'. So now only those that live with nature can speak to the gods and/or animals. Some trees grow tall creating darkness that scares men and they are not able to go near them. If they could they could again speak to the gods.